1. Field of the Invention
The present invention relates generally to methods and systems for the production of hydrocarbons, hydrogen, water, industrial raw materials, as well as rare earth and precious metals, basic chemicals and other products from various carbonaceous formations, such as those containing petroleum, oil sands, kerogen, bitumen, oil shale, lignite or coal.
2. Description of Related Art
Carbon-rich deposits found in subterranean (e.g. sedimentary) formations are commonly used as energy resources, raw materials and chemical feedstocks. In recent years, concerns over depletion of available hydrocarbon resources and the declining quality of hydrocarbons produced by traditional methods have led to development of processes that allow for more efficient recovery, processing and/or use of geologically derived hydrocarbon resources. Work conducted over the last century established the possibility of producing liquid or gas hydrocarbons from mineralized and entrained sources. With a few exceptions, the work largely failed the test of practicality.
Conventional crude oil deposits normally contain oil, water, and gas as three separate phases that are produced by multiphase fluid flow. In such multiphase fluid flow, the volumetric content, as well as differences in adherence, hydrophobic attraction, viscosity, surface area, interfacial tension, surface tension and solubility of materials plays an important role in the recoverability of the various materials. For example, differences in interfacial or surface tension between any two phases (and/or the materials within them) may interfere with the fluid flow of materials in one or more of these or other phases. This impedance may result in reduced relative permeability of the formation to at least one fluid phase. It may also reduce the effective permeability of the formation as a whole.
Other physical forces acting upon the multi-phase formation fluids also may impede mobility of such fluids in the formation. For example, interfacial tension between an oil droplet within the formation fluid and the mineral structure surrounding it acts to create a substantial capillary force that may act to retain the droplet in position. Acting across a formation, these localized interfacial behaviors may result in substantial non-recoverable, residual oil saturation left behind after the relative permeability to oil has been reduced to a low value. In addition, the differential viscosity and capillarity of each phase may cause interfingering (e.g. ‘channeling’) of flowing water and gas phases, thereby bypassing large segments of oil-saturated reservoir rock. This interfingering of flow is believed to account for a portion of the large residual, non-producible oil saturations remaining after depletion of most oil fields. Even after secondary and tertiary oil recovery technologies have been used, large volumes of oil, well over 50% of original oil-in-place, may remain in the depleted reservoir rock as non-recoverable oil. The methods of this invention apply to enhancing the recovery of hydrocarbon from these and other recalcitrant deposits.
In heavy oil and tar sand deposits, differential viscosity and capillarity problems in multiphase flow are often even more significant than conventional formations, resulting in both very slow production rates and very high residual oil left behind after depletion, even when the formation is relatively porous or permeable. Steam injection is often used to heat the heavy oil or tar/bitumen to reduce oil viscosity, increase the oil production rate and decrease the bypassed residual, non-recoverable oil saturation. Chemical agents that reduce interfacial tension and related capillary forces are also used to reduce the non-recoverable, residual oil left behind after depletion and abandonment. Even after reducing interfacial tension and decreasing viscosity by steam heating, substantial volumes of this oil still remains non-recoverable at economic rates, based on such multiphase fluid flow. The methods of this invention provide the means to enhance recovery of hydrocarbons from both conventional and nonconventional resources by use of formation permeability and an injected thermal energy carrier fluid (TECF) to mobilize hydrocarbons and establish both stable and transient in situ heating zones within target formations. In many cases, the heating zones comprise in situ heating elements described herein and in our previous applications.
Methods that reduce interfacial or surface tension, and the resulting impedance of flow that stems from it, are highly desirable in the field of hydrocarbon recovery and production. In situ methods for consolidating formation hydrocarbons into a single mobile fluid phase are of immense interest in the field of fuel and chemical production. It is also highly desirable to employ in situ methods that allow for production of formation hydrocarbons having a substantially narrower, and/or more defined, and/or more controlled range of compositions than is found using conventional petroleum and natural gas production technologies. Generally, methods that allow an operator increased control over the physical chemistry (including phase behavior) of formation fluids are of value in enhancing or enabling economic production. Similarly, methods that provide an operator with increased control of the chemical composition of the produced formation fluids are of great value provide opportunities to increase the value of the produced products.
The subject of this invention is the mobilization, transformation and recovery of carbon-based materials from various geological formations. While the focus of the present invention is recovery of hydrocarbons from carbonaceous resources having limited mobility, these methods apply equally to conventional gas and liquid petroleum formations as well. While not limited to solid phase deposits (such as oil shale and other kerogen-containing deposits) or high-viscosity (e.g. bitumen-rich) oil and tars, the present invention focuses on these as models of what is generally referred to herein as substantially immobile (or “fixed-bed”) carbonaceous materials. The formations or lithologic layers containing such materials may be referred to as containing fixed bed carbonaceous deposits; or as fixed bed hydrocarbon formations. Often, methods for developing formations containing substantially immobile hydrocarbon deposits fail the test of economic viability because they are not: a) effective at achieving high volumetric productivity, b) flexible with respect to in situ hydrocarbon chemistries and recovery methods, c) predictable and effective across a broad range of common geological formation conditions, or d) compatible with the effective protection of the surrounding environment and/or ecosystems. Nevertheless, recovering hydrocarbon products from mineral deposits such as oil shale, without costly and environmentally challenging mining operations remains a desirable objective in the field. The methods of the present invention focus broadly on the mobilization, fluidization, and in situ modification of carbonaceous deposits so as to provide an efficient means of producing useful fluid hydrocarbon products. Accomplishing this objective often requires methods that cause limited, but important changes in the chemical structure and/or physical state of the deposited resource in situ, i.e. in the formation. The present invention employs a variety of strategies to achieve economic productivity including in situ chemical reactions that change the structure or molecular weight of the carbonaceous material, changes in the solubility, density, viscosity, phase state, and/or physical partitioning of the hydrocarbon material within the formation or formation fluids. For the purposes of this invention a fluid may be, but is not limited to, a gas, a liquid, a supercritical fluid, an emulsion, a slurry, and/or a stream of solid particles or gelatinous materials that has flow characteristics similar to liquid or gas flow.
The methods of this invention provide a means to produce fluid hydrocarbon from formations comprising one or more fixed bed carbonaceous deposits (FBCD), and for extending high levels of protection to the surrounding environment by a combination of aquifer and water management methods, low-impact surface processing facilities, and a low-density distribution of surface wells and equipment. The invention further comprises both methods and systems that enable physico-chemical transformation of a wide range of carbon-rich deposits in situ followed by recovery of at least a portion of the produced hydrocarbons and/or other product materials at the surface. The methods allow production of various categories of products including: linear and cyclic hydrocarbons, linear and cyclic olefins, aromatic hydrocarbons, and other non-hydrocarbon products derived from formation minerals. For example, molecular hydrogen, metals (e.g. rare earth, precious and others) and metal salts, and other non-carbonaceous products also may be produced.
The methods of this invention apply to any carbon-rich geological formation, including but not limited to those containing deposits of: kerogen; bitumen; lignite; coal (including brown, bituminous, sub-bituminous and anthracite coals; liquid petroleum; depleted oil fields; tar or gel phase petroleum; and the like. Preferred applications include those wherein the carbonaceous materials are either mineralized (e.g. largely fixed in position), highly viscous, or rendered substantially immobile by entrainment in soils, sands, tars and other geological configurations that reduce transmissibility. For the purposes of this invention, all of these embodiments are said to represent fixed-bed hydrocarbon formations (FBHFs). The carbonaceous material itself may be referred to as fixed-bed hydrocarbon (FBH) even though it may exist in many forms, such as a soil-entrained fluid, a high-viscosity gel or fluid (e.g. tar), a mineralized, non-hydrocarbon solid (e.g. kerogen, lignite, coal, etc). Formations containing deposits such as these may be found at depths ranging from surface formations to tens of thousands of feet. FBH formations may be found under both land and sea surfaces.